Direct anterior hip replacement surgery, a type of total hip arthroplasty, is a minimally invasive surgical technique. With the direct anterior approach, surgery is performed through a natural space between the muscles of the anterior portion of the hip, rather than making the incision on the posterior side. That is, the hip joint is exposed between the anterior muscles without a need to separate tendons or cut tissues during this procedure. The portion of the upper thigh bone which includes the femoral head and neck and the hip socket which includes acetabulum are prepared for the insertion of the hip replacement implant once access to the hip joint is accomplished. The direct anterior approach has advantages in that damage of muscles or pain is decreased and healing time is relatively faster compared to posterior approach.
Various surgical instruments, such as a retractor, a starter reamer, and a broach, are used in the direct anterior approach total hip replacement surgery. Each of these instruments needs improvements to increase surgical efficiency in the direct anterior approach surgery. Necessary improvements are followed below.
I. Retractor and Saw
In total hip arthroplasty, different types of a saw, such as a power saw and a gigli saw, are being used to cut the femur, and a surgical instrument called a retractor is inserted in a surgical area and separates the surgical area by fixing surrounding muscles for preventing damage of the surrounding muscles. FIGS. 1a and 1b show a perspective view of and a top view of a retractor fixed for femoral resection where capsule 402 around a head of the femur 404 remains intact during direct anterior approach surgery.
When the power saw is used to cut a neck of the femur in the direct anterior approach, posterior capsule 402 is not resected and remains even after the neck of the femur 404 is resected. In this case, the head part of the femur 404 cannot be exposed. Removing the posterior capsule constitutes one of the most challenging steps in direct anterior approach surgery due to limited access and bleeding from femoral canal. Therefore, the gigli saw (not shown) may be used to solve such problem by simultaneously resecting the neck of the femur 404 and the surrounding capsule 402. However, delimiting an area to be resected is not simple and damage of surrounding muscles may occur even when the gigli saw is used.
Accordingly, there is a need to develop an instrument capable of minimizing damage to the surrounding muscles, facilitating delimitation of the area to be resected, and relatively easily resecting the neck and the capsule simultaneously.
In addition, as shown in FIGS. 1a and 1b, two retractors 406 are disposed facing with each other to separate the surgical area in the direct anterior approach surgery. Currently, fixing of the two retractors 406 is done by manpower. This additional manpower reduces surgical efficiency.
Therefore, there remains a need to develop a surgical instrument which can improve surgical efficiency by fixing the retractor in a different way without the need of additional manpower.
Moreover, muscle trauma (specifically TFL and gluteal muscles) is common when the direct anterior approach surgery is performed on a large, muscular patient. This damage usually occurs due to retractors or instruments used to prepare the femur for implant. Especially, prior narrow retractors place high force on a small area of the muscle and pull the muscle in direct contact, which becomes a major cause for muscle damage.
Hence, it is necessary to improve retractors to minimize damage to the surrounding muscle.
II. Starter Reamer
A starter reamer is used to enlarge a hole for inserting a femoral stem in direct anterior approach total hip replacement. The starter reamer has sharp teeth and a tough shaft. The sharp teeth are provided in a portion of the starter reamer, encountering the muscle in a moving path of the starter reamer, thereby causing muscle damage during the insertion process.
Accordingly, an improvement is required to prevent muscle damage when the starter reamer is inserted.
III. Broach
An artificial joint is placed between the femur and the pelvis in total hip arthroplasty, for which a surgical portion recessed by a certain size in the femur is formed to insert and fix the artificial joint. The surgical instrument used in this case is a broach.
The broach is coupled to a broach handle gripped by an operator. The terms of the broach and the broach handle are used interchangeably with a rasp and a rasp handle in the relevant industry. The broach and the broach handle will be used in the present disclosure.
Generally, a broach having a shape similar to the shape of a stem is used after the use of the starter reamer. Since the broach has sharp teeth, there is potential risk that the broach causes damage to the muscles when being inserted into a human body to create the surgical portion in the femur. Specifically, one part of the broach which is inserted in the bone does not damage the muscle, but another part of the broach which is exposed to the outside of the bone and contacts with the muscle causes muscle damage.
Therefore, the broach needs improvement to be safely used without causing muscle damage.
IV. Trunnion
Exposure of a trunnion of the femoral stem to the outside should be kept to a minimum until the femoral stem is completely inserted into the human body and the ball head is connected. Currently, the trunnion preparation is compromised by limited exposure, contamination by water insoluble substances and residual cloth fibers remaining after drying with sponges.
Therefore, an instrument capable of protecting the trunnion is needed.
V. Impaction Force
When a modular head is inserted in the hip joint, too much impaction force might cause fracture of the modular head, while too weak impaction force brings about a risk of premature separation after surgery. Thus, surgical failure rate can be decreased if the amount of impaction force to be applied in actual surgery can be measured before the insertion of the modular head. However, a device for quantitatively measuring the impaction force has not yet appeared.
Accordingly, there is a need to develop improved surgical instruments used in the direct anterior approach hip replacement surgery to resolve the abovementioned issues.